六自由度机械臂的运动学分析与Matlab仿真

本文以我公司6自由度机械臂为例,按照改进的D-H方法构建了6自由度机械臂工作运动的数学模型,对机械臂的正运动学、逆运动学进行分析。结合机械臂关节轴的典型几何结构,正向运动学分析通过各关节的关节角度求取末端机构的位置和姿态,逆运动学则利用代数法推导出封闭解,并给出了机械臂正逆工作方程的数学函数公式和运算求解的过程。通过MATLAB软件中的Robotics Toolbox,分别运算了机械臂的正、逆工作方程,进行了仿真实验。结果表明,函数测算结果与公式推导的数值基本一致,证实了模型结构和预算方法的一致性,对同类机械臂的研究具有很大的借鉴和参考价值。     

六自由度模块化机械臂工作空间量化对比分析*

针对六自由度模块化机械臂的两种不同构型,对其工作空间进行了量化对比分析。首先采用DH法进行了手臂结构建模,得到正运动学模型;然后基于MATLAB机器人工具箱搭建了两种构型手臂的仿真平台,运用蒙特卡洛法求解两种构型手臂的工作空间并采用可视化方法得到其工作空间的点云图,结合计算机辅助设计软件绘制两种手臂构型的3D工作空间,采用SLI指标对两种手臂构型的工作空间进行量化处理分析;最后通过对比两种手臂构型的工作空间点云图、3D工作空间实体和SLI指标性能分析了两种构型手臂的优劣,为后续的模块化机械臂的结构参数优化和空间灵活性研究奠定了基础。     

七自由度重载液压机械臂运动学仿真分析

针对7自由度重载液压机械臂,建立精确的重载液压机械臂系统运动学方程。利用Creo完成机械臂三维模型搭建。利用D-H参数法通过Matlab建立了机械臂的运动学模型,求解运动学方程完成了机械臂的正向运动学推导;通过蒙特卡洛法分析计算机械臂工作空间。为进一步研究动力学及运动精度控制提供依据。     

基于D-H算法的自主机器人机械臂建模方法研究

近年来,关于自主机器人机械臂控制的研究越来越多,如何快速、准确且平稳地抓取物体一直是研究的难点。用D-H建模方法对四自由度机械臂进行建模,给出了机械臂正运动学方程,并用代数法及几何法给出了机械臂逆解,算出了各关节变量值。最后,通过实验比较了两种逆解方法的有效性,使自主机器人机械臂的控制越来越准确、平稳。     

基于OpenGL的六自由度机械臂三维建模与仿真

针对六自由度机器臂,为了解决运动学分析结果不易验证以及在实体机械臂上演示成本较高的问题,设计了一套六自由度机械臂三维仿真软件.该软件以VS2008为开发平台,基于OpenGL函数库和Qt框架类,采用模块化的方法进行三维模型的创建,具有灵活性大、易于扩展的优点.结果表明,该仿真软件能够良好地仿真出机械臂的运动过程,对机械臂的研究和教学起到了促进作用.     

基于蒙特卡洛法的关节臂坐标测量机工作空间分析

传统的求解关节臂式坐标测量机工作空间的方法需要借助繁琐的数学公式、计算量大,针对这一问题选用蒙特卡洛法对工作空间进行分析;首先运用D-H方法建立关节臂式坐标测量机的数学模型得出运动学方程;然后采用蒙特卡洛法分析该测量机的工作空间,得出工作空间点云图;最后,采用局部象限分布的方法对关节臂式坐标测量机工作空间点云图的边界点进行提取;仿真实验结果表明用蒙特卡洛法对工作空间分析更简单易于实现,采用基于局部象限分布法提取到的边界点轮廓也更准确避免了虚假边界点的提取。     

果蔬采摘机械臂运动学分析

本文以自行研制的果蔬采摘机器人机械臂为对象,建立D-H运动学模型,对机械臂的正运动学与逆运动学进行求解分析,最后利用Matlab对其结果进行仿真,并与实际环境下机械臂的运动效果作比较,验证了模型的正确性,也为以后机械臂更复杂的操作与功能的拓展打下了基础。     

六自由度机械臂轨迹规划与仿真研究

针对六自由度链式机械臂在进行正运动学、逆运动学以及轨迹规划仿真时,不易直观地验证运动学算法的正确性和轨迹规划的效果,在正确建立机械臂数学模型的基础上,重点分析了机械臂在关节空间中轨迹规划的两种实现方法,并采用三维运动仿真进行了验证.开发了一套六自由度机械臂三维仿真软件,该仿真软件在VC++6.0开发平台上,首先利用分割类将基于MFC框架的窗口分割成为控制窗口和视图窗口两部分,然后利用OpenGL的图形库对机械臂进行建模,首次将正运动学、逆运动学以及轨迹规划算法融入其中开发而成.该仿真软件有效地验证了机械臂运动学模型建立的正确性,同时也对三次多项式和五次多项式两种轨迹规划方法做了直观的比较,结果表明后一种轨迹规划效果明显优于前一种.     

六自由度机械臂三维仿真软件的设计

在机械臂实体上进行正逆运算的结果往往难以分析和验证,且机械臂实体的成本比较昂贵,针对此问题,设计了一套六自由度机械臂的三维仿真软件,可以对机械臂的运动进行实时仿真。该软件以VS2008为开发平台,使用OpenGL函数库进行机械臂三维模型的创建,使用Qt界面库进行软件界面的设计,提供正逆解运算和演示。结果表明,该软件操作界面良好,能够很好地仿真出机械臂的运动过程。     

通用和修正D-H法在运动学建模中的应用分析

通用D-H法在机器人运动学标准建模中虽然已被广泛研究和应用,但其存在一个根本缺陷就是,对于两个相邻的平行关节,通用D-H法得到的齐次变换矩阵将是一个奇异矩阵,不能得到正确的模型,这样便无法对这部分关节运动进行正确的运动分析.而修正的D-H法是正对通用D-H所存在的缺陷进行了改进,保证了模型准确性.本文研究了通用的运动学建模方法D-H法和该方法的应用缺陷,以及修正的D-H法对通用D-H法存在的缺陷进行的改进,并对修正的D-H法在自由度串联机器人正逆运动学中建立模型的正确性进行了验证.     

一种六自由度机械臂的控制系统设计

针对机械臂在工业自动化等方面的需求,在分析了传统机械臂控制系统的基础上提出了一种以STM32F4为主控制器、陀螺仪传感器为关节状态检测器、舵机驱动模块为机械臂运动单元的六自由度控制系统。该系统采用扩展卡尔曼滤波算法(EKF算法),将陀螺仪采集的关节状态参数传递给EKF核心算法进行预估机械臂的运动状态,实现对机械臂运动过程中的偏差调控。实验表明,该控制系统的运动精度误差最大不超过18 mm,能够快速、准确地调控机械臂的运动轨迹。     

On the connectivity of manipulator free workspace

This article presents a new topological characterization of the free workspace of manipulators moving among obstacles. The free workspace is the set of positions and orientations that the end-effector of the manipulator can reach, according to the joint limits of each of its links, and taking into account the obstacles of the environment. A classification of new connectivity properties of the free workspace is proposed, corresponding to different types of motions (point-to-point motions, following of continuous trajectories) that the manipulator can perform in the Cartesian space. For each property, a necessary and sufficient condition is given, which permits verification of the connectivity of the whole free workspace and leads to all the connected subspaces in it. These properties have been implemented in a Robotics C.A.D. system using octree representation of spaces. Some applications are presented, which show that this work is of primary interest for preparing off-line tasks, and is a new contribution to the problem of robotic cell layout design.     

Position,Jacobian and workspace analysis of a 3-PSP spatial parallel manipulator

This paper investigates the problems of kinematics, Jacobian, singularity and workspace analysis of a spatial type of 3-PSP parallel manipulator. First, structure and motion variables of the robot are addressed. Two operational modes, non-pure translational and coupled mixed-type are considered. Two inverse kinematics solutions, an analytical and a numerical, for the two operational modes are presented. The direct kinematics of the robot is also solved utilizing a new geometrical approach. It is shown, unlike most parallel robots, the direct kinematics problem of this robot has a unique solution. Next, analytical expressions for the velocity and acceleration relations are derived in invariant form. Auxiliary vectors are introduced to eliminate passive velocity and acceleration vectors. The three types of conventional singularities are analyzed. The notion of non-pure rotational and non-pure translational Jacobian matrices is introduced. The non-pure rotational and non-pure translational Jacobian matrices are combined to form the Jacobian of constraint matrix which is then used to obtain the constraint singularity. Finally, two methods, a discretization method and one based on direct kinematics are presented and robot non-pure translation and coupled mixed-type reachable workspaces are obtained. The influence of tool length on workspace is also studied.     

Revolute manipulator workspace optimization: A comparative study

Robotic manipulators with three revolute families of positional configurations are very common in the industrial robots. The capability of a robot largely depends on the workspace of the manipulator apart from other parameters. In this work, an evolutionary optimization algorithm based on foraging behavior of Escherichia coli bacteria present in human intestine is utilized to optimize the workspace volume of a 3R manipulator. The proposed optimization method is subjected to some modifications for faster convergence than the original algorithm. Further, the method is also very useful in optimization problems in a highly constrained environment such as the robot workspace optimization. The test results are compared with standard results available using other optimization algorithms such as Differential Evolution, Genetic Algorithm and Particle Swarm Optimization. In addition, this work extends the application of the proposed algorithm to two different industrial robots. An important implication of this paper is that the present algorithm is found to be superior to other methods in terms of computational efficiency.     

Six-Dimensional space expression of workspace of six-DoF parallel manipulators using hyper spherical coordinates (HSC)

A closed-form formulation for the workspace of N-Degrees-of-Freedom (DoF) parallel mechanisms is presented using least-square curve fitting. The concepts of multi-dimensional polynomial (MDP) and in hyper spherical coordinates (HSC) are introduced. The boundary of workspaces of those parallel linkages which are surfaces without voids and concavities can be well approximated by the MDPs in the HSC. First, the boundary points are obtained in HSC considering all physical constrains and probable singularities. Then, an MDP with proper order consisting of sine and cosine functions is fitted to those points. The presented method is general and applicable to all DoF. Three case studies of 2, 3, and 6-DoF mechanisms are investigated to demonstrate the effectiveness of the method.     

Optimal design and workspace analysis of a mobile welding robot with a 3P3R serial manipulator

This paper presents the design optimization of a mobile welding robot based on the analysis of its workspace. A welding robot has been developed to be used inside the double-hull structure of ships, and it shows good welding functionality. But there is a need to optimize the kinematic variables ensuring that the required welding functions inside the ships are satisfied. The task-oriented workspace, which is the workspace enabling specific rotations, has been defined in order to validate the welding ability of the robot, and incorporating the required rotational capabilities. To calculate the workspace, a geometric approach is adopted which considers the pitching and yawing angles simultaneously. Based on the workspace analysis, a scenario is compiled for considering a mass reduction, and a ratio between the design parameters and the workspace, with constraints on the workspace margins. The proposed optimization procedure is composed of two steps of coarse and fine searching. In the coarse searching step, a feasible parameter region (FPR) is defined, which satisfies the geometrical design constraints, and can be obtained without any considerations of the objective functions. In the fine searching step, the design parameters are determined by using the optimization technique of the conjugate gradient method in the overall FPRs. The suggested approach to calculating the task-oriented workspace, and the procedure of optimal design, are expected to be applied to general industrial robots.     

Determination of workspace and required initial position of free-flying space manipulator at target capture

Consideration was given to the issues of computer-aided construction of the workspace of the free-flying space handling robot controlled in the class of feedback systems. In particular, a case was discussed where the information about the direction and distance to the target is acquired with the use of a camcorder with built-in range finder mounted on a gimbal attached to the robot body. The analytical relations obtained enable one to solve the problems of injecting the space robot into the zone of target location and maintaining the desired orientation of the body relative to the direction to the target. The proposed approach to the problem of generation of the workspace was implemented as a computer algorithm in the Matlab-Simulink environment. Operability of the algorithm was exemplified an arbitrary initial configuration of the robot.     

Intelligent collision avoidance planning of a robot manipulator whose workspace includes moving objects

The collision avoidance problem of a robot manipulator whose workspace includes moving objects is considered in this paper. It is shown that the proposed computer simulation system can be used in a dialogue mode with a designer to check whether or not collision with obstacles is avoided and to determine the appropriate movement.